U.S. Pat. No. 5,499,687 A discloses a downhole valve in the form of a bypass sub defined by a tubular casing. An opening is provided on one side of the casing for discharging fluid from the interior of the casing. The opening is normally closed by a sleeve which is slidably mounted in the casing. Rotation of the sleeve is prevented by a guide pin extending radially inwardly through the casing into a longitudinally extending slow in the outer surface of the sleeve. The sleeve is biased to the closed position over the opening by a helical spring which extends between a shoulder on the sleeve and an annular ledge above the guide pin. During a lost circulation, i.e. when it is desired to inject lost circulation material into the formation, the drillstring is broken at the surface and a plastic ball is placed therein. The ball engages an inwardly inclined shoulder on the interior of the sleeve. A pump pressure in the drillstring causes the ball to push the sleeve downwardly against the force of the spring until the shoulder engages the ledge. In this position, the openings in the sleeve and in the casing are aligned so that lost circulation material can be discharged into the formation surrounding the casing.
U.S. Pat. No. 6,155,350 A discloses a ball seat which is be held in place by one or more shear pins or other fixation devices or by the nature of assembly. A breakable device, such as a rupture disc, is in communication above the ball and with an enlarged piston area below. When the breakable member or rupture disc breaks, the applied pressure is translated to a far larger piston area, and the shear rating of the shear pin or pins is almost instantaneously overcome. Thus, the pressure at which the ball seat releases is determined by the design and rating of the breakable member or rupture disc.
WO 2004/022907 A1 relates to a ball operated bypass tool with a ball catcher.
U.S. Pat. No. 6,820,697 B1 relates to a fluid flow actuator downhole tool configurable in at least a first tool configuration and a second tool configuration. The tool comprises a tubular housing and an activating sleeve, the housing being adapted to catch a sleeve when the sleeve is dropped from surface and the engagement of the sleeve with the housing permitting actuation of the tool between the first and second tool configurations. A flow restriction is provided for permitting fluid flow actuation of the tool when the activating sleeve has been caught in the body.
In view of the above-described situation, there exists a need for an improved technique that enables to provide a downhole valve with improved characteristics.